In response to the ever increasing demand for novel compounds useful in the effective treatment of various disorders, a variety of strategies for discovering and optimizing new therapeutics has been developed. For the most part these strategies are dependent upon techniques that allow identification of molecules binding to a given biological target.
In one such strategy, novel drugs are identified by screening compound libraries and determining which compounds have the highest therapeutic properties, and optimizing such properties by synthesizing structurally related analogs. The limitation of such an approach is that it is possible to synthesize and test only a very small subset of all possible molecules thereby resulting in a high probability that the most efficacious molecules will be missed.
In another approach novel drugs are identified by determining structure activity relationships (SAR) correlating a common structural feature of the molecule to target based biological activity. While widely used this method does not always yield active analogs indicating SAR alone may not be sufficient to warrant biological activity in all cases.
SAR activity by NMR as described in U.S. Pat. No. 5,698,401, relates to a process for identifying compounds which bind to a specific target molecule. In this approach the physical structure of a target protein is determined by nuclear magnetic resonance analysis (NMR) and the small molecule building blocks are identified that bind to the protein at nearby points on the protein surface. Adjacently binding small molecules are then coupled together with a linker in order to obtain compounds that bind to the target protein with higher affinity that the unlinked compounds alone. Thus, by having available the NMR structure of the target protein, the lengths of linkers for coupling two adjacently binding molecules can be determined and small molecules can be rationally designed. Although these methods are powerful they have serious limitations, such as the required amounts of target protein and the fact that the protein must be 15N-labeled to be useful for NMR studies.
With the advent of combinatorial chemistry and high throughput screening, numerous high-profile reviews have appeared in the literature that classify and prioritize the chemical space for drug discovery. Lipinski et al., Adv. Drug. Deliv. Rev., 3-25, 1997, is a widely cited review that correlates physical-chemical properties of permeability and absorption with biological activity. This review defines the “rule of 5” which a molecule should generally not violate to be granted the status of “drug-like” molecule. The “rule of 5” states that poor absorption or permeation are more likely when there are more than 5-H bond donors (expressed as the sum of OHs and NHs); more than 10 H-bond acceptors (expressed as the sum of Ns and Os); the molecular weight is over 500; and the log P is greater than 5.
Ghose et al., J. Comb. Chem., 1, 55-68, 1999, provides an analysis of some computable physical-chemical properties and chemical constitutions of known drug molecules available in the comprehensive Medicinal Chemistry (CMC) database and seven known drug classes. Their study showed qualifying ranges for calculated log P, refractivity, molecular weight, and total number of atoms.
In recent years, electronically active molecules, such as antioxidants and reductants, have been recognized as functioning in redox regulation of key biological processes such as immune response, cell-cell adhesion (e.g. atherosclerosis), cell proliferation, inflammation, metabolism, glucose uptake (diabetes), and programmed cell death (apoptosis).
It has been described in the art, that biological activity of certain compounds is related to their capacity to accept one or two electrons to form the corresponding radical anion or dianion, and that the electron-accepting capacity of these substances can be modified by directly adding substituents to the core structure. For these types of compounds, the attracting or donor effects of the substituents are very important in affecting the redox properties of the core structure system, either facilitating or interfering with the electron transfer, (see for example a study of the substituent effect on the redox properties of the quinone moiety, Aguilar-Martinez et al., J. Org. Chem., 64, 3684-3694, 1999). If a molecule's core structure is affected by its substituents, a change of its voltammogram may occur representing a change in electron transfer (redox) properties.
The redox behavior of a series of structurally related flavonoids under physiological conditions has been investigated by Hodnik, W. F. et al, Biochem. Pharmacol., 37 (13), 2607-11, 1988, as well as the relationship of flavonoids oxidation potential and effect on the hepatic metabolism, see Hendrickson, H. P. et al., J. Pharm. Biomed. Anal.,12(3), 335-41, 1994. Half peak oxidation of flavonoids was measured and correlated to LPO inhibition data in Saskia et al., Free Radic. Biol. Med., 20 (3), 331-342, 1996, and the redox intermediates of flavonoids and caffeic acid esters from propolis were studied by cyclic voltammetry, see Rapta, P. et al., Free Radic. Biol. Med., 18(5), 901-8, 1995.
Structural activity relationship studies on apomorphine and its derivatives have been described by Lashuel, H. A. et al., Journal of Biol. Chem., 45, 42881-42890, 2002, hereby incorporated by reference in its entirety.
Ashnagar A. et al., Biochim. Biophys. Acta, 801, 351-9, 1984, have described the measurements of reduction potentials of hydroxy-1,4-naphthoquinones and hydroxy-9,10-anthraquinones as well as the corresponding methoxy- and acetoxyquinones, and the role of internal hydrogen bonding and its bearing on the redox chemistry of the anthracycline antitumor quinones. The correlation among antitumor activity, quinone reduction potential and the logarithm of the partition coefficient (log P) was obtained by Kuntz et al., J. Med. Chem., 34, 2281-6, 1991. The relationships of reductive potential, kinetics of enzymatic reduction, augmented oxygen consumption and cytotoxicity were determined for seven clinically relevant mitomycin antibiotics by Pan S. S. et al., Mol. Pharmacol., 37, 966-70, 1997. Twelve 1,4-naphthoquinones were tested against the ascetic form of sarcoma and it was shown by statistical analysis that the most important molecular parameters determining their effectiveness in prolonging the life of mice bearing this tumor were their redox potentials, see Hodnett E. M. et al. J. Med. Chem., 26, 570-4, 1983. Electrochemical properties of some biologically active quinone derivatives, furanquinones, pyridoquinones and diplamine, a cytotoxic pyridoacridine alkaloid, have been reported in Crawford, P. W. et al., J. Electrochem. Soc., 144, 3710-3715, 1997, indicating a possible relationship between reduction potential and anticancer activity.
Cyclic voltammetry has been used for the detection of compounds in different solutions, see for example, Kilmartin, P. Antioxidants and Redox Signaling, 3, (6), 941-955, 2001, and in a redox control and monitoring high throughput screening platform used in conjunction with another detector, (see U.S. Application 2002/0123069), but heretofore cyclic voltammetry has not been used for the a priori identification of possible therapeutic candidates.
It is evident that there is a need for novel techniques useful for rapidly and efficiently identifying molecule compounds that are capable of having a therapeutic effect.
It has been surprisingly found that novel therapeutic molecules can be identified by their physical-chemical properties comprising a least one redox parameter and falling within a range predefined by the physical-chemical/biological relationship of a previously tested small subset of compounds with the same core structure.